This invention relates to lasers that produce coherent radiation that has a shorter wavelength than the wavelength of the pumping radiation, and more particularly to lasers that use a rare earth doped solid state lasing medium under ambient temperature conditions to provide upconverted laser radiation from the ultraviolet through the infrared portions of the electromagnetic spectrum.
Laser systems that produce wavelengths in the blue and green portions of the visible spectrum are highly desirable for a variety of applications. These applications include laser based video display systems and optical systems wherein the higher resolutions afforded by short optical wavelengths are important, such as optical storage systems.
Although laser systems have been developed that produce outputs in the blue and green portions of the visible spectrum, the value of such systems have been diminished by one or more factors that include high cost, critical alignment and high maintenance. For instance, rare gas ion lasers have both a high purchase price and a high degree of maintenance. Frequency doubling or summing lasers that employ a nonlinear element require critical alignment and high maintenance. Also, systems that use non-coherent pumping sources, such as flash lamps and arrays of semiconductor diodes, are impractical for efficient upconversion systems.
A laser source that uses solid state components throughout and employs a single diode laser pumping source is a desirable configuration for a low cost, low maintenance system, but such lasers-have never been able to achieve operation in the blue and green regions of the visible spectrum under normal ambient temperature operating conditions. Furthermore, the prior art has not been able to achieve such operation With a continuous or quasi-continuous coherent pumping source.